1. Field of the Invention
The present invention relates generally to an adjustable apparatus for cleaning and polishing rolls used to roll sheet stock, such as sheet steel, sheet plastic, paper, and the like. In particular, the invention pertains to a roll assembly cleaning and polishing device having a pivoting polishing block of improved durability, which also minimizes uneven wear of both the polishing block and the roll.
2. Description of the Prior Art
Sheet stock, such as steel, plastic, aluminum, and paper, is generally fed through a series of rolls, such as guide rolls and wringer rolls, as part of the manufacturing process. Such rolls provide contact with the sheet stock for a variety of purposes, such as to guide or dry the sheet stock either before or after a coating process, as it is being cut to width, or as it is wound into large coils for ease of handling, storage, and transportation. The surfaces of such rolls have a tendency to accumulate abrasive contaminants, corrosive coatings, and particles of sheet stock on their surfaces, which can seriously mar and damage the surface of the sheet stock. Furthermore, such accumulations on the roll surfaces may embed themselves in the roll surfaces, scar the roll surfaces, or otherwise seriously damage them. It is therefore desirable to clean the surfaces of the rolls to prevent such accumulations from damaging both the sheet stock and the rolls themselves.
Although it is possible to shut down a manufacturing operation periodically to replace the rolls with fresh ones that have been cleaned, or to clean manually the rolls in service, it is generally uneconomic to do so, because the down-time involved to stop and start the manufacturing operation is excessive.
Consequently, a roll cleaning apparatus which functions during the manufacturing process is preferred. One such cleaning system is described in Applicant's U.S. Pat. No. 4,528,716, which relates to a roll cleaning device utilizing a knife-edge blade arrangement to clean the surface of roll assemblies. However, this device does not provide a mechanism for polishing the rolls, nor does it provide a means for oscillating the blade arrangement across the surface of the roll.
An early attempt to provide a roll cleaning and polishing device employed a series of polishing blocks arranged on a polishing block support assembly in a tandem block arrangement having a total combined width at least as wide as the roll surface, and mounted tandem to a lever operated engagement system so that the operation of the lever engages the polishing blocks over the entire width of the roll surface. The polishing blocks are each resiliently mounted so that they provide substantially the same surface pressure within a wide range of variation of polishing block wear between the individual polishing blocks. This system is not entirely satisfactory, however, because the stationary polishing blocks so used have a tendency to leave a scarring pattern of their own on the roll.
An improved roll cleaning apparatus is described in Applicant's U.S. Pat. No. 4,841,675. This patent discloses a device which automatically engages and oscillates a tandem arrangement of polishing blocks on the roll surface. The oscillating motion of the blocks laterally scrub the roll surfaces as they polish to prevent the development of any polishing block scarring pattern. The oscillating movement is provided by a pneumatically actuated positioning cylinder at one end of the tandem polishing block arrangement on its polishing block support assembly and a hydraulically operated dampening cylinder at the other end. Each of the cylinders is individually supported in position with its own pneumatic support assembly. This arrangement provides automatic alignment of the polishing block support assembly with the roll surface at a regulated pressure. Further, separate cylinders for each end of the polishing block support assembly prevent bearing misalignment problems.
Although this apparatus is quite satisfactory from the standpoint of performance, it is bulky, complex and expensive. Accordingly, Applicant provided a further improved apparatus, disclosed in U.S. Pat. No. 4,887,329, which utilizes a support assembly that is retained by self aligning bearings, in order to permit reciprocal actuation by a single linear actuator coupled to one of the ends of the support assembly. The device therefore enables a simple, single end actuation of the polishing blocks, by means of a lever or counterweights, depending on whether temporary or continuous engagement of the polishing action is desired.
Despite the foregoing efforts, certain difficulties continue to be encountered in the operation of roll cleaning and polishing devices. For example, polishing blocks have conventionally been bonded to their block mounting surface brackets by adhesive bonding, using a high strength glue or epoxy resin. Upon exposure to certain chemical environments, the bonding material sometimes fails, causing the polishing block to fall off its mounting bracket. In some cases, the rolls present a pinch point where, for example, a steel strip is translated across the roll and snubbed to this roll by means of a snubber roll. If a dislodged polishing block travels across the roll in the direction of the pinch point, it may be pulled through the rolls and/or the strip. Consequently, in the case of electrogalvanize line conductor rolls, if the strip is temporarily separated from the conductor roll by the polishing block, arcing will occur, resulting in damage to or destruction of the conductor roll.
Another problem characteristic of conventional roll cleaning and polishing devices relates to the difficulty of properly aligning the bank of polishing blocks in horizontal relation to the roll. In this regard, polishing blocks have conventionally been rigidly mounted to the end of a torsion arm. It has therefore been necessary to accurately hold individual polishing blocks in a horizontal plane while tightening a bolt to secure the polishing block. This task is difficult to perform correctly, since the resilient joint of the torsion arm does not rigidly support the torsion arm while the bolt is being tightened. As a result, installed polishing blocks are commonly slightly out of horizontal alignment. Thus, upon displacement of the torsion spring shaft during operation of the cleaning/polishing device, the forces applied by the polishing block to the face of the roll are not uniform.
Consequently, non-uniform contact causes the blocks to wear unevenly, and sometimes to wear the roll surface unevenly, which imparts undesired hills and valleys in the roll profile. In the case of electrogalvanize line conductor rolls, altering the roll profile prevents the strip from following the contour of the roll, thereby introducing air pockets between the strip and the roll. Such air pockets become the source of arcing, which as noted previously can damage or destroy a conductor roll.
It would therefore be desirable to provide an apparatus for cleaning and polishing roll assemblies which overcomes the aforementioned difficulties of the prior art.